The three-dimensional structures and functional characterization of sets of alternatively spliced variants will provide insight into not only the mechanism of alternative splicing, but also its biological role and function. The feasibility of developing an understanding of alternative splicing will require structural data from a relatively large number of proteins, and thus, success depends upon the ability to determine high-resolution three-dimensional structures rapidly. In addition, crystallography approaches can be used to study protein-ligand interactions and protein-protein interactions to further the understanding of the difference in properties of a set of altematively spliced variants. The specific aims for accomplishing this are: (1) analyze methods for prescreening protein and protein solutions that will facilitate protein crystal growth, investigate procedures for rapidly screening crystal growth conditions, evaluate optimization methods for the production of crystals for diffractions studies, and develop procedures for determining the appropriate cryoconditions for x-ray data collection; (2) develop automated protocols for phase determination, structure fitting and structure refinement to minimize time and effort required for this process and evaluate approaches for determining phases by incorporation of an anomalous scatterer (MAD) or by more traditional approach of determining a structure using traditional derivatives (SIR/MIR); and (3) use crystallographic approaches to study protein-ligand interactions and protein-protein interactions to develop an understanding of difference in function of alternative splicing variants. The key to rapid structure determination protocols will be to integrate the methods for crystallization, data collection, phase determination, map fitting, and refinement. The integration and streamlining is fairly straightforward, but does offer numerous challenges. At each step problems can arise requiring that one go back to previous steps to make adjustments in the protocols to surmount barriers to the structure determination.